Stretching apparatus



Dec. 1-3, 1949 v. H. HA SSELQUIST 9 STRETCHING APPARATUS I Filed June 14, 1945 t 2 She'e'ts-Sheet l MEL Z/ZJZ'DA H3595 EZ L/[Ef Dec. 13, 1949 v. H. HASSELQUIST 2,491,041

' STRETCHINRG APPARATUS 2 She ets-Sheet 2 Filed June 14, 1945 w NN ILH a HL/EfZZZL 7 75555] Patented Dec. 13, 1949 STRETCHING APPARATUS Victor H. Hasselquist, Akron, Ohio, assignor to The B. F. Goodrich Company, New York, N. Y., a corporation of New York Application June 14, 1945, Serial No. 599,490

5 Claims.

This invention relates to apparatus for stretching sheet material and is especially useful for stretching elastic covers such as. ice-removing covers about or along the surfaces of airfoils.

Elastic ice-removing covers have been secured aboutv the leading edges of the wings and other parts of aircraft by rows of hollow tubular rivets secured to the skin of the airfoil and having threaded bores for securing screws. The covers have been provided with rows of apertures along their margins for receiving fastening screws adapted to enter the threaded. bores of the rivets, and fairing strips of sheet material, also having apertures for engaging the same screws, sometimes have been applied over the margins of the covers.

Stretching of the covers to secure them in place under tension without damage to the covers or to the surfaces to be covered has been a difiicult problem, especially where the parts are of large size. Where ice-removing covers are to be applied these have often had air connections integral therewith which had to be inserted through apertures therefor in the skin of the airfoil causing further difficulties in assembly. By the present invention an improved apparatus is provided for facilitating the assembling operation. The apparatus is also useful wherever a covering; is to be stretched along a surface to which it is to be attached.

Objects of the invention are to provide uniform stretching of a margin along a surface; to provide for permitting the application of one margin of the coverin in advance of entry of the air connections; to provide for application of the cover at any position or attitude of the airfoil;- to provide for clamping the margin and uniformly stretching the covering from one end of the covering to the other, and to provide for applying the, cover with the least amount of manual exertion.

These and other objects will appear from the following description and the accompanying drawings.

Of the drawings;

Fig. 1V is a perspectivev view of a. portion of. an airplane showing an ice-removiug covering attached to the leading edge of the wing. parts of the plane being broken away.

Fig. 2 is a perspective view of a section of the leading edge of the wing showing one margin of apparatus secured to the wing and to the clamping means in position to stretch the coverin about the leading edge of the wing.

Fig. 4 is a similar view showing the covering stretched into place and temporarily secured by a holding pins, the stretching apparatus being also I line 6-6 of Fig. 6A.

- the stretching means in place on the surface to be covered.

Fig. 8 is a side elevation partly in section of a modified clamping means.

Fig. 9. is a detailed View of a movable jaw and cam bar thereof.

Fig. 10 is a section taken on line Ill-40 of Fig. 8.

Fig. 11 is a side view partly in section of another modification of the clamping means.

Fig. 12 is a detailed view thereof.

Fig. 13 is a sectional view taken on line 13, I3 of Fig. 11.

Referring to the drawings and first to Figs.

-- 1 to 7 thereof, which show a form of apparatus constructed in accordance with and embodying the invention, the numeral l0 designates the skin of the plane about which the stretchable covering H is to be applied. As shown in Figs. 2., 3 and 4. one margin i2 of the covering has been secured to the wing by screws l3 passing through apertures in, said margin and entering the threaded apertures of hollow threaded rivets l4 secured to the skin of the wing. A fairing strip [5. has also, been applied. over the margin and is held by the .same screws. The opposite margin Iii-of the covering is securedto a clamping means I] which extends the length of the covering and ships the margin throughout its length by clamping pressure, by pins 18 entering some of the apertures of a row of apertures l 9 extending along the wing at the position of desired attachment of the unsecured margin are a plurality of stretching means 20 as seen in Fig. 3. The stretching means Removably secured to the wing the beaded reinforced margin l6 of the cover- Y ing I is clamped by a movable jaw 21 in the form of a bar extending loosely through the hollow enclosure of the bar 25. A third bar 28 extends through the hollow enclosure of the bar 25 between it and the movable bar 21. The bar 28 is of substantial semi-circular cross-section and when rotated acts as a cam to force the movable jaw 21 against the fixed jaw 26, this being due to the semi-circular form of the bar which in one rotative position has its flat side facing the inner face of the bar 25 opposite to the jaw 26 and thereby releases pressure against the movable jaw 21, whereas in another rotative position, shown in Figs. 5 and 6, it presents greater depth and wedges the movable jaw 21 against the fixed jaw. Rotation of the cam bar 28 may be accomplished by a handle 29 fixed to the bar at its flat side and extending through a clearance notch 30 in the wall of the bar 25. A fixed handle 3| may be secured to bar 25 adjacent the handle 29 to assist in rotating the bar 28, the arrangement being such that the operator may grasp both handles with one hand for application of clamping pressure.

Referring to Fig. 6 which shows the stretching means in section, this comprises a bar having an angular foot 36 fixed thereto, the foot having a pin |8 extending therefrom adapted to enter the threaded aperture of a hollow rivet 38 to which the margin I6 is to be attached. A carriage 39 is slideably mounted upon bar 35 and for this purpose is provided with a friction block 40 secured thereto as by screws 31 and having an aperture 4| adapted to pass over the bar 35. The carriage 39 is formed with a clearance opening 42 about the rod 35. A second friction block 43 has an aperture 44 for receiving the bar 35 therethrough and is mounted in a U-shaped stirrup 45 having a handle 46 attached thereto. The stirrup 45 is pivoted as at a pin 41 to the block 43. A coil spring 48 mounted between the carriage 39 and the block 43 urges the block 43 normally to the left as seen in Fig. 6 and thereby causes the block 43 to frictionally clamp the bar 35.

For facilitating free movement of the block 43 along the rod 35 in one direction while providing for gripping of the rod when the block is urged in the opposite direction by the movement of a force applied at a position spaced-apart from the center line of the rod 35, the aperture 44 is formed with a chamfer 50 at its upper left-hand side and a chamfer 5! at its lower right-hand side as seen in Figs. 6 and 6A, the arrangement being such that when a force is applied along the rod 35 at the pivot pin 41 in a direction to the right of Figs. 6 and 6A, the corners, provided by the intersections of the chamfers 59, 5| with the walls of the aperture 44, will frictionally grip the rod and prevent movement along the rod, and when such force is applied at the pivot pin 41 in a direction to the left of Fig. 6, pressure on the corners will be relieved and a long bearing surface o he aperture 44 will be presented to the rod 35 permitting sliding movement of the block along the rod. The aperture 4| of the block 40 is similarly formed with a chamfer 52 at its upper left side and a chamfer 53 at its lower right side which provide for gripping of the rod 35 by the block 40 when a superior force is applied to the block 49 at a position near the pivot pin 55 as by pressure of the clamping bar 25 due to tension of the covering in the direction to the right of .Fig. 6, and permitting sliding of the block 40 along the rod in a direction to the left of Fig. 6 when a superior force is applied at the pivot pin 55 acting in a direction to the left of Fig. 6. The legs of the stirrup 45 are pivotally connected as at 56 at a position less remote from the handle 46 than pivot pin 41 to a pair of links 51 which in turn are pivotally connected to the block 40 at the pivot pin 55. The carriage 39 is formed with a horizontal extension 58 parallel to the rod 35 and terminating. in a' downwardly projecting portion 59. The arrangement is such that the projecting portion 58, the portion 59 and the block 49 provide a notch adapted to confine the clamping bar 25 with one face of the bar resting against the block 40 near the pivot pin 55.

When the pin I8 secured to the rod 35 is engaged in an aperture in the skin of a plane and the clamping bar 25 is engaged in the notch of the stretching means with the margin l5 of the covering clamped by the clamping means, the carriage 39-may be shoved along the bar 35 in a direction to the left of Fig. 6 until the covering is 'underslight tension. This movement may readily be accomplished by hand manipulation. With the covering slightly tensioned, a force will be applied to the block 49 in a direction to the right in Fig. 6 in the region of the clamping means or near the pivot pin 55, thereby tipping the stretching means slightly with relation to the rod 35 and causing the block 40 to grip the rod. Further tensioning of the covering may then be accomplished by first moving the handle 46 to the right which will cause the handle to pivot about the pivot pin 56 and to apply a force in a direction to the left at the pivot pin 41 to the block 43. This will move the block 43 bodily to the left in Fig. 6 along the rod 35 to a new position. Movement of the handle 46 is then reversed and pressure applied thereon in a direction to the left whereupon the block 43 will grip the rod 35 under the off-center pressure of the spring 48 and handle 46 will pivot about the pivot pin 41 thereby moving links 51 to the left of Fig. 6 which in turn will overcome the gripping force due to the tension of the covering and move the block 49 and with it the carriage 39 to the left to a. new position with further tensioning of the covering. In other words by reciprocating the handle 46, a walking movement of the blocks 40 and 43 along the rod 35 is provided, and the covering is drawn into a position where the apertures in its margin coincide with the apertures in the skin of the plane and screws or temporary studs may then be inserted through the apertures of the covering and through the apertures of the skin of the plane to hold the covering in place.

As shown in Figs. 2 to 4 a plurality of clamping means may be distributed along the clamping bar so as to apply tension at a plurality of positions simultaneously and by substantially simultaneous operation of the stretching means the margin of the covering may be drawn into position in a single operation without damage to the covering such as might result by local stretching. When the covering has been secured by screws,

the tensioning means may be released by apply.-

ing. a tipping force to the carriage $8. asby tappingit with a. hammer or applying such movementby use of a lever or a wrench applied to the carriage. This may conveniently be accomplished by a stop-pin on the carriage adapted tn contact the stirrup 45- when the handle @16- is moved to the right in Fig. 6 beyond such movement as. is necessary to accomplish the walking. movement. I

The pin l8 which holds the boot 3%. of the rod 35 to the threaded aperture of the rivet 33' may be constructed as shown in Fig. 7 wherein the pin comprises a portion of such small diameter as to pass endwi'se through the threaded aperture and having threads 62 on one side of the pin adapted to be engaged by the threads of the rivet whenthe pin is moved in a direction toward such threads. Such a pin has threaded engagement with the rivet at the side toward the tensioned covering and prevents slipping of the tensioning means from the covering o' f the plane.

Referring to Figs. 8 to 10, which show a modifled form of clamping means, a tubular bar 65 of rectangular cross section and having a longitudinal opening 66 along one corner thereof encloses a pair of bars 61, 58 extending longitudinall thereof. Bars 61, 68 have complementary saw-tooth cam surfaces 69, ill respectively. Bar

61 is formed with a movable jaw Sid and the tubular bar 65 is formed with a cooperating fixed jaw H. The two jaws are adapted to grip the margin of a covering preferably back of a beaded edge thereof and are so formed as to provide a clearance space 12 therebetween for receiving 5 such beaded edge. The cam surfaces of the bar 61, 68 are so inclined that relative movement of one of the bars longitudinally of the other will cause their cam surfaces to force the bars apart when the movement is in one direction and will permit them to move toward each other when the movement is in the opposite direction. Such relative movement is provided for by screws I3, 14 which engage threaded openings l5, 16 respectively in opposite ends of the bar 58. The enlarged heads of these screws are adapted to overlap and engage the ends of the bar 67. The arrangement is such that by turning the screw 13 in a direction to enter the threaded opening the movable jaw 10 will be moved toward the fixed jaw II and will grip the margin of the covering. When the covering is to be released the screw 13 may be screwed outwardly and the screw 14 may be screwed into the aperture it and its enlarged head engaging the bar Bl will force the bar down the inclined cam surface moving the movable jaw Hi away from the fixed jaw II and releasing the covering.

Referring to Figs. 11 to 13 of the drawings which show a still further form of clamping means, this apparatus is provided with a tubular bar 81 of rectangular cross section having a longitudinal opening 8! near one corner thereof, the tubular bar providing a stationary jaw 82 therealong adjacent the opening. Mounted within the hollow passage of the tubular bar 89 for movement with respect thereto are a pair of bars 83, 84 having cooperating cam projections 85, 86 thereon at intervals along their length. The bar 84 is formed with a movable jaw 81 adapted to cooperate with the fixed jaw 82 in clamping the margin of the covering, the jaws also being formed to provide a clearance cavity 88 therebetween back of the jaws for receiving the beaded margin of the covering.

when the bar- 83, is moved longitudinally of.

tubular bar with respect; to. bar 8t,v the cam 93 at 95 and their other ends are pivotally secured as at 91 to a lug 98 fixed to the bar 80 adjacent the slotted opening 90. The arrangement is such that when the lever 93 is moved to the left in Fig. 11 to its full line position the block 9|, andwith it the cam bar 83, is moved to the right as shown in Fig. 11, thereby forcing the movablejaw 81 toward the fixed jaw 82 and clamping the fabric, and when the lever 93 is moved to the dot and dash line position of Fig. ll, the clock GI, and with it the cam bar 83, are moved to the left of the figure to the dot and dash line position, thereby releasing the margin of the covering.

These and other variations may be made Without departing from the invention as it is defined on a surface having corresponding apertures at said position for receiving fastening means for securing the covering, thereto, said apparatus comprising a rod having means for attaching it to said surface at said desired position, includin an element insertable in one of the apertures of said surface, with the rod extending toward a margin of the covering to be attached at said position, a clamping bar arranged to extend along said margin and having means to grip an extensive portion of the margin of said covering and means movable along said rod and engageable with said clamping bar for stretching said covering to said position.

2. Apparatus for stretching a covering having marginal apertures to a desired position upon a surface having corresponding apertures at said position for receiving fastening means for securing the covering thereto, said apparatus comprising a rod having means for attaching it to said surface at said desired position, including an element insertable in one of the apertures of said surface, with the rod extending toward a margin of the covering to be attached at said position, a clamping bar arranged to extend along said margin and having means to grip an extensive portion of the margin of said covering and means movable along said rod and engageable with said clamping bar for stretching said covering to said position, said means to grip the margin of the covering comprising jaws engageable with a substantial portion of said margin, and cam means for moving one of said jaws toward the other.

3. Apparatus for stretching a covering having marginal apertures to a desired position upon a surface having corresponding apertures at said position for receiving fastening means for securing the covering thereto, said apparatus comprising a rod having means for attaching it to said surface at said desired position, including an element insertable in one of the apertures of said surface, with the rod extending toward a margin of the covering to be attached at said position, a clamping bar arranged to extend along said margin and having means to grip an extensive portion of the margin of said covering and means movable along saidrod and engageable with said clamping bar for stretching said covering to said position, said means movable along said rod comprising a carriage slideable along'said rod, and means on said carriage for advancing it along said rod in step-by-step movements.

4. Apparatus for stretching a covering having marginal apertures to a desired position upon a surface having corresponding apertures at said position for receiving fastening means for securing the covering thereto, said apparatus comprising a rod having means for attaching it to said surface at said desired position, including an element insertable in one of the apertures of said surface, with the rod extending toward a 1 margin of the covering to be attached at said position, a clamping bar arranged to extend along said margin and having means to grip an exten-l sive portion of the margin of said covering, and means movable along said rod and engageable with said clamping bar for stretching said covering to said position, said means movable along said rod comprising a carriage, a plurality of gripping members on said carriage adapted to frictionally grip said rod, and means on said carriage for alternately advancing said gripping members.

5. Apparatus for stretching a covering having marginal apertures to a desired position upon a surface having corresponding apertures at said position for receiving fastening means for secur- 0 ing the covering thereto, said apparatus comprisa a ing a rod having means for attaching it tolsaid surface at said desired position, including an element insertable in one of the apertures of said surface, with the rod extending toward a margin of the covering to be attached at said position, a clamping bar arranged to extend along said margin and having means to grip an extensive portion of the margin of said covering, and means movable along said rod and engageable with said clamping bar for stretching said covering to said position, said means movable along said rod comprising a carriage slidably engaging the rod, a pair of blocks thereon having aligned apertures for receiving said rod, said blocks being frictionally engageable with said rod when urged therealong in one direction by a load applied thereto at a position spaced from their apertures and in a direction substantially parallel to said rod, and means for alternately so loading one block and relieving the other to advance said carriage along said rod in step-by-step movements.

VICTOR H. HASSELQUIST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 458,682 Fleischmann Sept. 1, 1891 7 693,227 Brannon Feb. 11, 1902 769,994 Fererro Sept. 13, 1904 843,603 Hemenway et a1 Feb. 12, 1907 2,378,011 Hasselquist June 12, 1945 

